Hardened material for creating seaweed bed

ABSTRACT

To provide a hardened material for creating a seaweed bed that can efficiently supply ferrous ions to organisms. Cement, steel and iron slag crushed to 40 mm or less, decomposed hardwood chips on the order of 20 to 80 mm, and water are mixed, and the obtained mixture is cast into a formwork. The mixture is then cured within the formwork until it hardens. Next, the concrete obtained by being hardened within the formwork is crushed so as to have a mass per unit volume of 2 to 3 tons/m 3 , whereby a concrete block for creating a seaweed bed whose surface shape is of natural stone is obtained

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a hardened material for creating a seaweed bed. More particularly, it relates to a hardened material for creating a seaweed bed that is dropped into the sea and serves to create a seaweed bed.

(2) Description of Related Art

In recent years, a phenomenon called “rocky shore denudation” has caused severe damage to fisheries etc., where seaweed, such as Laminaria japonica (konbu) and Undaria pinnatifida (wakame), growing in shallow sea areas have diminished, and a hard shell-like seaweed of pale pink called coralline algae (calcareous algae) covers the entire surface of rocks on a seabed.

More specifically, coralline algae covering a seabed secrets from the surface thereof a substance to prevent other seaweed from adhering and exfoliates superficial cells so that other seaweed cannot grow on their bodies, and thus it becomes difficult to recover large-sized algae (a seaweed bed disappears) when rocky shore denudation occurs. Then, as a result of disappearing seaweed beds that are hideouts and egg-laying sites of small fish, small fish and large-sized fish that prey on small fish no longer approach, so that the catches have decreased year by year.

Moreover, disappearance of the seaweed beds results in not only a loss of habitat and egg-laying sites of a multitude of marine animals including fish but also a loss of plant population that is very important to sea ecosystems for photosynthesis, so that sea ecosystems have been greatly affected.

As one of the causes of rocky shore denudation, there has been mentioned “ferrous ions (Fe²⁺)” of which seaweed is likely to absorb having conventionally been supplied from forests through rivers to the sea, whereas the supply of ferrous ions has decreased in recent years due to logging of forests and construction of dams, etc.

To cope therewith, for example, JP2640926(B) discloses a sunk block for which a groove-like recess portion having a large edge angle is formed on the surface of a block body and one or more relatively small grooves are provided adjacent to the groove-like recess portion, and a plate-like breeder material formed by mixing a glassy material having an iron content containing divalent iron and cement mortar and hardening the mixture is disposed in the groove-like recess portion.

Moreover, JP2002-45078(A) discloses a block prepared by mixing 70 to 30% by mass of blast furnace slag and 20 to 10% by mass of coal ash in 10 to 60% by mass of molten sulfur and molding and solidifying the mixture.

SUMMARY OF THE INVENTION

However, even when, as in the inventions of JP2640926(B) and JP2002-45078(A), ferrous ions ingestible for phototrophs such as seaweed are eluted, the ferrous ions are likely to be oxidized by oxygen in water, and become ferric ions to promptly settle out as Fe₂O₃, so that it becomes impossible for the organisms to ingest the same.

The present invention has been made in view of the above problems, and an object thereof is to provide a hardened material for creating a seaweed bed that can efficiently supply ferrous ions to organisms.

In order to achieve the above-mentioned object, a hardened material for creating a seaweed bed of the present invention is a hardened composition containing a solidification material, steel and iron slag, wood chips, and water.

Here, fulvic acid is released from the wood chips, the fulvic acid is bound with ferrous ions released from the iron and steel slag, and stable iron fulvate that is water soluble, long-lived, and unlikely to be oxidized in seawater can be generated.

Moreover, if the hardened material for creating a seaweed bed of the present invention has a mass per unit volume of 2 to 3 tons/m³, the hardened material for creating a seaweed bed is unlikely to roll even in the presence of waves, which is preferable.

Further, if the hardened material for creating a seaweed bed of the present invention has a surface shape of natural stone, a gap is likely to be formed when the hardened materials for creating a seaweed bed are piled up, and hence it is likely that fish inhabit there.

Moreover, in the hardened material for creating a seaweed bed of the present invention, if the composition contains excretion, the excretion contains protein, amino acids, urea, uric acid, etc., and thus generates ammonia when being decomposed, and the ammonia is complexed with ferrous ions released from the steel and iron slag, so that a substance that is unlikely to be oxidized as with iron fulvate can be generated.

Moreover, in the hardened material for creating a seaweed bed of the present invention, if the solidification material is cement, the hardened material can have a high strength as compared with the use of other solidification materials.

Moreover, in the hardened material for creating a seaweed bed of the present invention, if the wood chips have at least partially decomposed, fulvic acid is likely to be released, and as a result of the wood chips decomposing to disappear, pores are formed at the position of wood chips to make the hardened material porous, so that unevenness is formed on the surface of the hardened material to make it likely that seaweed seeds adhere thereto.

Moreover, in the hardened material for creating a seaweed bed of the present invention, if the composition contains leaf mold, fulvic acid is also released from the leaf mold, so that more iron fulvate can be generated.

Moreover, in the hardened material for creating a seaweed bed of the present invention, if the composition contains charcoal, fulvic acid is also released from the charcoal, so that more iron fulvate can be generated.

The hardened material for creating a seaweed bed according to the present invention can efficiently supply ferrous ions to organisms.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an example of construction where a hardened material for creating a seaweed bed of the present invention is used as underwater armor stone.

FIG. 2 is a schematic view showing an example of construction where a hardened material for creating a seaweed bed of the present invention is used as an underwater reef construction material.

DETAILED DESCRIPTION OF THE INVENTION

A hardened material for creating a seaweed bed of the present invention is a hardened composition containing a solidification material, steel and iron slag, wood chips, and water.

Here, as the solidification material, although a common solidification material can be used, cement is preferable because this results in a relatively high strength of the hardened material.

The steel and iron slag is iron and steel by-products produced in an iron and steel manufacturing process, and includes converter slag, pretreatment slag, decarburization slag, dephosphorization slag, desulfurization slag, desiliconization slag, electric furnace reducing slag, electric furnace oxidizing slag, secondary refining slag, teeming ladle slag, etc. One of these or two or more as a mixture can be used.

Moreover, the steel and iron slag contains ferrous (FeO and Fe₃O₄) that is likely to be oxidized and unstable. In particular, the converter slag contains ferrous at 20%, is easily supplied because of a large amount of generation, has a high degree of solubility of iron ions, and is therefore preferable as a material from which ferrous ions are eluted.

Ferrous is likely to be eluted in the course of oxidation underwater, and is absorbed in organisms in the form of ferrous ions, while ferrous is a very unstable substance.

Moreover, the wood chips, which are chips of a waste wood or the like, decompose to release fulvic acid. Because the fulvic acid is water soluble, has a carboxyl group and a carbonyl group, and has an iron binding function, iron ions bind with the fulvic acid, so that iron fulvate that is stable even under water is generated.

Moreover, because the wood chips decompose to release fulvic acid, it is preferable to use wood chips that have at least partially decomposed.

Moreover, the composition mentioned above can further contain leaf mold and charcoal (for example, wood charcoal).

Moreover, the solidification material, the steel and iron slag, the wood chips, and water may be compounded at any ratio, however, for example, in the case of 1:10:4:1.5 for solidification material:steel and iron slag:wood chips:water, a hardened material with voids formed to some extent and having a high compressive strength can be obtained.

FIG. 1 is a schematic view showing an example of construction where a hardened material for creating a seaweed bed of the present invention is used as underwater armor stone. In addition, FIG. 2 is a schematic view showing an example of construction where a hardened material for creating a seaweed bed of the present invention is used as an underwater reef construction material.

Cement, steel and iron slag crushed to 40 mm or less, decomposed hardwood chips (which is an example of wood chips.) on the order of 20 to 80 mm, and water were mixed, and the obtained mixture was cast into a formwork. The mixture was then cured within the formwork until it hardened. Next, the concrete obtained by being hardened within the formwork was crushed so as to have a mass per unit volume of 2 to 3 tons/m³, whereby a concrete block for creating a seaweed bed (which is an example of a hardened material for creating a seaweed bed.) 1 whose surface shape is of natural stone was obtained.

However, the mixture is not necessarily cast into a formwork and cured within the formwork, as long as the mixture can be hardened.

The obtained concrete blocks for creating a seaweed bed 1, as shown in FIG. 1, were dropped into seawater 2, and bedded so as to cover the top of ripraps or the like as armor stone. Growth of seaweed 3 could be confirmed on the concrete blocks for creating a seaweed bed 1 after about one to two months since the bedding.

Moreover, concrete blocks for creating a seaweed bed 1 obtained in the same manner, as shown in FIG. 2, were dropped into seawater 2 and piled up as a reef construction material. Growth of seaweed 3 could be confirmed on the concrete blocks for creating a seaweed bed 1 after about one to two months since the piling.

Moreover, winding a seed string adhered with seaweed spores around a columnar hardened material for creating a seaweed bed of the present invention and arranging the hardened material for creating a seaweed bed of the present invention wound with the seed string on the concrete block for creating a seaweed bed 1 shown in FIG. 1 and FIG. 2 after seaweed sprouts have grown about 10 cm from the wound seed string makes the seaweed more likely to increase.

Moreover, for example, pouring seawater containing seaweed spores in a tank and further placing a string in the seawater allows obtaining a seed string adhered with the seaweed spores.

Because iron fulvate is originally generated in humus soil of a forest, it tan also be considered to put humus soil in a bag or the like permeable to seawater and also put steel and iron slag as appropriate so as to form a sandbag, and then drop the sandbag containing humus soil into the sea so as to create a seaweed bed, however, as is apparent from the application when constructing a bank, it is hard to form a gap between sandbags even by piling up the sandbags, and moreover, even if wood chips mixed in the humus soil decompose, the sandbag has not solidified, and thus the sandbag containing humus soil does not become porous as in the case where wood chips in concrete have decomposed.

In contrast thereto, the concrete block for creating a seaweed bed of the present invention has solidified, and the surface shape is of natural stone, and thus when the concrete blocks for creating a seaweed bed are piled up as shown in FIG. 2, a gap is formed therebetween, so that it becomes likely that fish inhabit in the formed gap. Moreover, also in the concrete block for creating a seaweed bed itself, as a result of the wood chips decomposing to disappear, pores are formed at the position of wood chips to make the concrete block for creating a seaweed bed porous, so that unevenness is formed on the surface of the concrete block for creating a seaweed bed to make it likely that seaweed seeds adhere thereto.

As in the above, because the concrete block for creating a seaweed bed of the present invention is a hardened composition containing steel and iron slag and hardwood chips, fulvic acid is released by the hardwood chips, and the fulvic acid is bound with ferrous ions released from the steel and iron slag, so that stable iron fulvate that is water soluble, long-lived, and unlikely to be oxidized in seawater can be generated, and accordingly, the ferrous ions can be efficiently supplied to organisms in the form of stable iron fulvate.

Moreover, because the concrete block for creating a seaweed bed of the present invention has a mass per unit volume of 2 to 3 tons/m³, when the concrete block for creating a seaweed bed is arranged in the sea, the concrete block for creating a seaweed bed is unlikely to roll even in the presence of waves.

Further, because the concrete block for creating a seaweed bed of the present invention is a hardened composition containing decomposed hardwood chips, fulvic acid is likely to be released, and as a result of the hardwood chips decomposing to disappear, pores are formed at the position of hardwood chips to make the concrete block for creating a seaweed bed porous, so that unevenness is formed on the surface of the concrete block for creating a seaweed bed to make it likely that seaweed seeds adhere thereto. 

1. A hardened material for creating a seaweed bed, which is a hardened composition containing: a solidification material; steel and iron slag; wood chips; and water.
 2. The hardened material for creating a seaweed bed according to claim 1, having a mass per unit volume of 2 to 3 tons/m³.
 3. The hardened material for creating a seaweed bed according to claim 1, having a surface shape of natural stone.
 4. The hardened material for creating a seaweed bed according to claim 1, wherein the composition contains excretion.
 5. The hardened material for creating a seaweed bed according to claim T, wherein the solidification material is cement.
 6. The hardened material for creating a seaweed bed according to claim 1, wherein the wood chips have at least partially decomposed.
 7. The hardened material for creating a seaweed bed according to claim 1, wherein the composition contains leaf mold.
 8. The hardened material for creating a seaweed bed according to claim 1, wherein the composition contains charcoal. 